I headcanon that Plague dragons have no table manners and no one in Plague really gives a shit about silverware. When out-of-flight dragons visit for important meetings, trade routes and other exchanges, plague dragons display a very forced semblance of self-restraint. But as soon as they’re gone they order the kitchen to just dump what’s left on the table and everyone digs in.
Plague feasts are messy, messy affairs, and it’s considered a bonding practice to fight over and exchange meals. The highlight of these occasions is when someone releases a large, living animal– pigs and chickens are good for poorer clans, with some clans using elephants– and the entire party helps kill it before tearing into it.
The leftover remains of this last, large meal are used as party favours.
(As for non-meat eaters, they still help kill the animal, but are usually provided their own selection of food.)
(Although I’m pretty sure all Plague dragons have modified digestive tracks, and thus eat meat even if their species as a whole usually doesn’t.)